Abstract : Four Al-Mg-Li alloys were investigated for potential use in high performance aircraft. Ingot casting was very difficult. Fabricating was also difficult; however, a limited amount of sheet and some upset forgings were fabricated. Solution heat treatment practices providing highest strength were determined and aging surveys for each alloy were conducted. Cold working between solution heat treatment and artificial aging significantly affected response to artificial aging. Elastic moduli were higher and densities were lower than those of other aluminum alloys. Elevated temperature strengths were comparable to those of 2020-T6. Resistance to exfoliation corrosion was comparable to 7075-T76 sheet, but the alloys were highly susceptible to stress-corrosion cracking. Toughness of these alloys was also very low. (Modified author abstract)